Holmium (Ho), thulium (Tm), and chromium (Cr) doped yttrium aluminum garnet (Ho:Tm:Cr:YAG) laser operates at a wavelength of 2.09.mu.. Although, in the host YAG crystal Ho is codoped with Tm and Cr, the laser is called Ho:YAG because 2.09.mu. is a Ho fluorescence line. This 2.09.mu. wavelength is considered eye-safe and therefore, is considered useable for commercial laser radar applications.
In order to use the laser in a heterodyne detection mode, it is required to operate at a narrow bandwidth. Generally, such a narrow line width laser is a called a single frequency laser, and this invention relates to the reduction of laser line width to accomplish obtaining a high energy single frequency laser source. Presently, a high power, high repetition rate, single frequency Ho:YAG laser does not exist. Low power, continuous wave (CW) lasers are under development at various laboratories at the time of this invention.
It is an object of this invention to present a method and apparatus for providing a high power, high repetition rate, single frequency laser source.
Another object of the present invention is to present a method and apparatus for providing such a high power single frequency laser source for use in eye-safe conditions.
A further object of this invention is to present an invention which provides a method and apparatus for a high power, eye-safe, single frequency laser source for use in interferometric detection systems in atmospheric and laser radar applications.